Germans didn't use proxy fuzes. However, I think the 88mm could use a bit of work (and thats based purely from offline target practice, which is always easier than in the servers).
Perhaps give each gun possition a battery of 3 FlaK 36's to control, not counting the one you're in, with the shell randomization, and the slaved gun's fuze distance being relative to the main cannon in the battery, but min/max distances maintained for each gun (so that each gun in the battery can only fuze its shells for a maximum of 5000yds from its own possition), and maybe reduce the minimum minimum fuze distance to 600yds so as to provide a viable self-defense from strafing aircraft.